A typical loading dock of a building includes an exterior doorway with an elevated platform for loading and unloading vehicles, such as trucks and trailers. To compensate for height differences between the loading dock platform and an adjacent bed of a truck or trailer, many loading docks have a dock leveler. A typical dock leveler includes a deck or ramp that is pivotally hinged along its back edge to vary the height of its front edge. An extension plate or lip extends outward from the deck's front edge to span the gap between the rear of the truck bed and the front edge of the deck. This allows personnel and material handling equipment to readily move on and off the vehicle during loading and unloading operations.
The deck is usually moveable between a stored position and an operative position. Depending on the style of dock leveler, the deck may store either vertically or horizontally. U.S. Pat. No. 6,502,268 shows an example of a horizontally storing deck, and U.S. Pat. No. 5,396,676 discloses a dock leveler with a vertically storing deck.
Vertically storing decks are usually driven by a hydraulic cylinder. The hydraulic cylinder typically extends to raise the deck to its vertically stored position and retracts as the deck descends to its operative position. The force for lowering the deck can come from the hydraulic action within the cylinder and/or the weight of the deck itself. In some cases, the deck's weight urges the deck downward while a hydraulic flow restriction associated with the cylinder provides the deck with controlled descent.
The hydraulic cylinder can also be used for holding the pivotal deck at its vertically stored position. A pivotal anchor point of the cylinder, the pivotal anchor point of the deck, and the pivotal connection between the deck and the cylinder can be positioned so that the deck is vertical when the cylinder's piston rod bottoms out (i.e., the piston rod fully extends to the end of its stroke). When stopping and holding the deck in this manner, however, the radial pin clearance at the various pivotal connections allows the deck to rock back and forth before the deck settles to a completely stationary, upright position.
The temporary rocking motion may exert undo stresses and/or wear at the pin joints and related components. Moreover, when servicing or repairing the dock leveler, it may be desirable to have a redundant or more positive locking mechanism for holding the deck upright.
Consequently, a need exists for a better stop and/or locking mechanism for holding a dock leveler's deck at a vertically stored position and selectively securing it for service and repair work.